A McCormick-type knotting device forms a loop of the tie, which can be either a metal wire, a filament twine, or even a synthetic-resin filament, that seures together a bale of hay, straw, or similar crop, around a knotter and then pulls this loop off the knotter automatically as the bale is pushed out of the machine. The tie ends held in the holder disks are released, but only the new section of the tie in the holder is cut. After rotation of the knotter a short and a long tie end are under the knotter upper jaw so that pulling the loop off the knotter automatically forms a loop that then must be drawn between the lower and upper jaws of the knotter. To this end the end of the upper jaws is inclined so that it holds the loop tightly and lets the other part go. Cutting the one tie section is done by a stationary blade as it is pulled past the rotating tie holder so that tie sections held in the knotter are not subject to excessive tension.
A Deering-type knotting device forms a knot in the tie and has tie-holding disks rotatable about a horizontal axis adjacent the trailing bale end and a knotter rotatable about a vertical axis upstream of this trailing bale end. After each tying operation the free end of the tie is left in this holder and this tie extends downstream over the leading end of the bale and then back along underneath it. At the trailing bale end the tie passes through a needle which can engage up behind the bale when the plunger of the baling machine has compressed it downstream. When the needle does this it engages a portion of the tie in the holder, which rotates as the needle withdraws so that the tie is very tightly held around the bale.
The knotter is provided immediately adjacent this holder and has, relative to its vertical axis lying generally at the trailing bale end, upper and lower radially extending jaws, the lower of which is fixed and the upper of which is shaped like a hook and pivotal toward and away from the lower jaw. The knotter first rotates with the two jaws together to loop the two strands of the tie around itself, but on returning opens its two jaws so the strands are caught between them. This leaves a complete loop of both strands of the tie wound around the two jaws with the two ends then passing between these jaws. The ties are then cut between the knotter and the holder and the loop is pushed off the knotter, releasing the double overhand knot thus formed. This effectively and neatly knots the ends of the portion of tie snugged around the bale. The entire operation is wholly automatic, very fast, and quite smooth. Simple cams acting on the needle, holder, knotter, and knife displace these elements wholly pivotally for perfectly synchronous operation.
With the Deering system, therefore, the tie is held by the hooked end of the upper jaw, not by spring tension. A stripper pushes the tie loop off the knotter jaws. Thus the tie is suddenly snapped tight when it is cut free, subjecting the knotter to considerable shock. It is therefore standard practice to incline the lower holding edge of the upper jaw relative to the direction the tie is tensioned in to minimize the shock to the system. Unfortunately such a system can lead to jamming, which can cause considerable damage to the machinery.
Accordingly East German Pat. 111,770 of H. Prellwitz and G. Muller proposes a system wherein the upper jaw has a tooth or hook that engages in a relatively deep groove in the lower jaw. If more than two strands of the tie are captured between the jaws, they do not close and can be pulled therefrom.
Although this system offers several substantial advantages over the other prior-art ones, it does not work well when a thin synthetic-resin tie is used. Such a filament is very hard to cut, so it must be held very tightly before the blade is effective on it. Thus the tie must be very tightly gripped, making its removal from the knotter even more difficult. The lower stretch of the tie therefore can break and remain jammed in the knotter, so that as the bale is pushed out the knotter is bent and damaged. In general such extra tensioning of the filament makes it much more difficult to push off the knotter.